"Perpetual" Dear Science, Why is..... thread.

We have multiple perpetual threads across all the fora, threads that allow congregation and aggregation along a set topic. It strikes me that The Observatory could use a perpetual thread, where Sciencey questions can be asked / discussed / debunked in general terms.

Energy costs are set to rise, quite sharply in some instances, over the next few decades, nuke plants being taken offline either from age or policy (germany), a big rise in coal burners and a suddenly dependance on LPG/shale gas. We can all play our part in reducing energy use, unplugging things, insulation, using energy efficient lightbulbs/other equipment, but it strikes me that we waste unholy amounts of energy every single day.

Streetlights - our cars have onboard lights, why do we need sodium lamp style lights every N feet, couldnt we skip every other one and still provide enough light? Obviously in pedestrian areas this doesnt follow as for 'safety' (read crime) you`ll want lots of light, but on motorways /freeways / high ways/dual carriageways, especially when there will be low or no pedestrian impact, why are we wasting so much energy? Its not just the wasted energy costing us $ per minute, its the light pollution which blots out the sky for miles around, the having to create and maintain infracstructure to throw that light. It does seem logical to me that turning off half of the lights, even staggering the on/off so that they dont double up on each side but instead overlap, has the potential to save significant amounts of money, both in direct spend and in future savings, at very little cost.

Another (stupid) thought that occurs to me, we're talking about carbon capture and recycling, but theres no effort spent to recover wasted light energy or limit the expenditure. I know photovoltaic technogloy is inefficient, only generating a small fraction of the actual solar energy hitting it, we have phones that can run off a solar charge, radios that will pull down enough juice in a 20mx20mm space to not just operate but put a tricklec charge into the battery. It just seems mad that we're blasting all this energy around and making no attempt to recover it, you`ll never get to the perfect balance, the perpetual motion machine as it were, but even 5% recovered or saved, when you look at the bigger picture, is an immense amount of energy.

Street lighting prevents accidents especially those involving pedestrians and cyclists etc but also on motorways.

The cost of the infrastructure to capture and reuse this energy will vastly outweigh the benefits, and could be better spent making the systems more efficient (LEDs, Insulation, smart devices with energy management or smart systems which monitor and adjust to conditions, think only turning on the lights in a certain radius of highway traffic at quiet times like 3am)

The amount of energy there is negligible. Perfectly monochromatic green light at 555nm, lighting one square metre to 100 lux (quite bright) is about 15 milliwatts. This means that your highway lighting - we'll be generous and give it a uniform 50 lux (typical room lighting) - has about 5 milliwatts per square metre. 5% of that, recovered or saved, is nothing. Solar irradiance has 500-1,000 watts (a million times more) per square metre.

You've fallen into a trap where your logarithmic senses work against you.

All of those streetlights blaring away are using significant amounts of power in totality - so the 'light pressure' (brain isnt firing right today) doesnt look like it`d be worth attempting to capture even on a mssive scale. Fair enough, but given that, is there a point where (re)capture become viable? Or is `daylight` ie 100kK-lux the baseline.

Also, similarly along the lines of recovery/capture - computers dump out lots of waste heat via air convection, even with water pupmps the eventual outcome is radiating heat out to the surrounding atmosphere. How feasible would taking the waste heat and using it to drive a small stirling engine, or using some form of heat-exchange to generate electricity (obviously at mili and micro levels). Obviously data centers already do this to a greater (and lesser) degree, this is more shrinking it down to the consumer level - use the power return to help condition/shape the power already applied or diver it for use charging smartphones

My maths are awful, last kilojoule calculation I remember doign was setting fire to a peanut to figure out its calorific energy worth, so in my head a cpu/gpu cranking at anywhere up to 100C (under load) should be able to do more with that energy use than just be a glorified noise maker/space heater.

Theres a stupid amount of money in process refinement, saving even 0.1% can have a huge impact, it seems a lot of 'regular' consumers thoughts stop and end with putting plastic in the right bin and ensuring you recycle. I guess Im coming at it from a 'grey' water concept, we flush away gallons upon gallons of pure, clean, safe _drinking_ water to carry away our waste - using the water you just washed your hands in _as part_ of the flow that flushes away your waste rather than an additional couple of gallons, seems to me, to be eminently sensible and sustainable. Likewise with light/heat waste, we're making strides in conservation by double/triple glazing, void insulations and the like, switching to low power idle units - but the process refinements can only get back so much before we have to change the what we do, not just the how. Hence my question about recovering 'waste' streetlight

I've often wondered why there aren't efforts made to capture expended energy at the gym. You have all of these machines telling you that you're burning so many watts, why not try and capture that?

It seems to be significant too. It's not uncommon to maintain 100 watts for an hour, which that could power *something*. That's just 1 person's contribution. At my gym there must be 50 people working out at any one time, on average.

It's not a technical problem of "why can't we recapture waste energy?". It's an economics problem of "is it worth recapturing this waste energy?".

For most of the applications suggested here, the cost of recapturing the energy is so high that it simply doesn't make sense. Even from an environmental perspective, I suspect that in many cases the overall impact (including the cost of materials, construction, infrastructure and maintenance) makes it an environmental negative too.

I've often wondered why there aren't efforts made to capture expended energy at the gym. You have all of these machines telling you that you're burning so many watts, why not try and capture that?

It seems to be significant too. It's not uncommon to maintain 100 watts for an hour, which that could power *something*. That's just 1 person's contribution. At my gym there must be 50 people working out at any one time, on average.

Don't the machines themselves usually run off their own motion? Isn't that why they usually shut off quickly once you stop moving?

As for the streetlights, I have seen some of them in my area (SF Bay Area, CA) being replaced by what look like LED streetlights, which presumably use a lot less energy, and should also last longer before burning out. They seem quite a bit brighter than the sodium lamps, as well. The replacement seems really slow, but theoretically we should realize a lot of energy savings eventually.

Now, my question: why do we have 8 blood types? It seems like we would have one, or millions -- like DNA. And we have 8 types, but we can't use animals blood. How is that not weird?

For people, it seems tied to resistance to various diseases. This is per a Scientific American article.

Type A makes you resistant to some stuff, Type B makes you resistant to other...turn evolution loose and there you go.

Kinda like sickle cell anemia being present in areas where there is alot of malaria risk.

Also, having different types among a group of humans makes sure that anything that is blood borne (or carries info from your blood) can't be transferred to another person with a different blood type, because it gets attacked pretty aggressively.

There's actually more, but in the pioneering work 100 years ago with the equipment and samples available that's what was figured out.

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LED streetlights, which presumably use a lot less energy, and should also last longer before burning out. They seem quite a bit brighter than the sodium lamps, as well. The replacement seems really slow, but theoretically we should realize a lot of energy savings eventually.

Low pressure sodium lamps are far and away more energy efficient than anything else, the drawback being the light quality - it's largely monochromatic smeared around the sodium emission lines.

You can be A or not A, B or not B, and Rh+ or Rh-. Lack of A or B is signified by O, both is AB. But it is 3 essentially independent factors that can have two different states, giving 2^3 combinations. Hence the 8 blood types rather than 7 or 9. And there are many more that aren't important enough to write on a donor card, so we actually have lots of blood types, we just don't bother to distinguish between them.

But breaking it down into the 3 factors helps explain why you can give O- blood to anyone, and people who are AB+ can receive any blood. But AB+ blood can only be given to AB+, and O- can only receive O-. Because you cannot give blood containing A, B or Rh bits to someone who does not have it already.

Matter of fact, I have an idea for an experiment involving, say, Seaworld dolphins. Separate one from the rest of them into a side pool, direct it to tell a specific other dolphin to do a specific trick. Send him back in to the main pool with the rest of them, see what happens. Rinse, repeat. Or, tell one to have another retrieve an object for the trainer. This is something that's intrigued me for a long time.

Dolphins are trained by conditioning, similar to dogs. Having one tell another what to do is a level of abstraction that we haven't been able to achieve in our communications with them. Regardless of what it said about their ability to communicate with each other, our ability to communicate with them on a more abstract level would itself be a major breakthrough.

It's amazing to me that a number of animals have learned a subset of a human language: dogs, birds, dolphins. A well trained, intelligent animal can correctly retrieve the red ball rather than green one for example, based only on the spoken command. Humans on the other-hand have been less successful in learning any animal languages. We know some animals must have complex languages, I doubt african gray parrots would evolve the abilities that let them learn English so well if all they sang in the wild was no more nuanced than "this is my territory, and a female should come mate with me".

Getting even this much of a grasp of a truly alien language is really exciting. I really hope that in a few years somebody can start breaking it out into the grammar they use; nouns, verbs, etc. It will be fascinating to see of other species languages are structured anything like human languages are.

I don't dispute this -- but why even those numbers? I understand the theory of disease behind them (but those seem a little weak -- why would it prevent A working with B).

The ABO(rh) system works by antigens. Mboza is touching on the answer, as Rhesus is a modifier in this system, so one can be one of the following:A+, A-, B+, B-, AB+, AB-, O+ and O-.

It's what your immune system recognises as foreign. If you have O blood, then your blood does not have anything that will trip the immune system of anyone else at this level. If you have A blood, then anyone without A themselves will recognise your blood as foreign, likewise with B blood. Someone with AB blood is a pretty useless donor, for example, as only someone else with AB can accept your RBCs, but you can accept everyone else's.

Someone with O blood is tricky on the operating table, while blood of O is common, she will reject blood from all other groups.

So O is the universal donor, AB is the universal acceptor. Rh factors are somewhat minor to this, but are much more complex: There are around 60 Rh blood types. The five main Rh antigens are often called "D" and it gets even worse from here.

In general, it's best to "play along with" the major antigen types, and to match Rh + or -.

My mother is O+ (I was never typed) so if I'm A+, then I can accept her RBCs, but she cannot accept mine.

I don't dispute this -- but why even those numbers? I understand the theory of disease behind them (but those seem a little weak -- why would it prevent A working with B).

The ABO(rh) system works by antigens. Mboza is touching on the answer, as Rhesus is a modifier in this system, so one can be one of the following:A+, A-, B+, B-, AB+, AB-, O+ and O-.

It's what your immune system recognises as foreign. If you have O blood, then your blood does not have anything that will trip the immune system of anyone else at this level. If you have A blood, then anyone without A themselves will recognise your blood as foreign, likewise with B blood. Someone with AB blood is a pretty useless donor, for example, as only someone else with AB can accept your RBCs, but you can accept everyone else's.

Someone with O blood is tricky on the operating table, while blood of O is common, she will reject blood from all other groups.

So O is the universal donor, AB is the universal acceptor. Rh factors are somewhat minor to this, but are much more complex: There are around 60 Rh blood types. The five main Rh antigens are often called "D" and it gets even worse from here.

In general, it's best to "play along with" the major antigen types, and to match Rh + or -.

My mother is O+ (I was never typed) so if I'm A+, then I can accept her RBCs, but she cannot accept mine.

Aaand it is pretty much reversed for plasma donation, just to confuse things more.

Dogs understand the concept of vision, they can understand when you point at something, when fetching or playing they`ll drop the item where theyre (observably) sure you can see it. They can also understand verbal commands and gesture commands, service dogs for example are 'smart' enough to be able to assist in operating an ATM or supermarket self checkouts.

As for red/green, its a conditioning response, if you keep showing them a bright pink ball and call it 'green ball' then tell the dog to fetch the geren ball.. it`ll bring that one because thats what its associated with the noise/gesture youve trained it with. Its a conditioned response, very pavlovian, even complex statements like 'go to the kitchen, get the dish, bring it here' - the dog understands the training word kitchen, the object dish and the command bring. It doesnt understand what a kitchen is, who made the dish, what its made of or why you want it to bring it.

As for red/green, its a conditioning response, if you keep showing them a bright pink ball and call it 'green ball' then tell the dog to fetch the green ball.. it`ll bring that one because thats what its associated with the noise/gesture youve trained it with. Its a conditioned response, very pavlovian, even complex statements like 'go to the kitchen, get the dish, bring it here' - the dog understands the training word kitchen, the object dish and the command bring. It doesnt understand what a kitchen is, who made the dish, what its made of or why you want it to bring it.

If you teach a human that pink is 'green' its' whole life and you tell it to fetch the 'green ball' you'll wind up with the pink one too.

And I'm pretty sure a dog understands that the word 'kitchen' represents that room where food comes from. You know, like it is. It's not a big stretch from understading the difference between 'inside' and 'outside'.

I'll give you that it probably doesn't understand that the dish was made of cheap plastics in Taiwan, though.

Point being, the above seems exceedingly dismissive in an age when we are realizing that our dismissive attitudes regarding non-human intelligence is precisely why we have not recognized the actual capabilities and potential of non-human intelligence as well as a very incomplete idea of the concept of intelligence itself.

They're not really colorblind, just much lower visual acuity than humans.

Which is why I didn't say they're colorblind. They're not, however they are red/green colorblind. They have two types of cones instead of three like humans, which almost exactly duplicates the effect of red/green colorblindness in humans.

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Even at grayscale differentiation based on luminance is possible.

The same is true of humans with red/green colorblindness, assuming there actually is a difference between the red and green shades in question.

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And then there's their sense of smell, they very well could smell the chemical differences between red and green pigment compounds.

Fair enough, but that doesn't exactly make "red ball" and "green ball" a useful way to differentiate them, does it? Why not "tuna ball" and "chicken ball." When performing a test on the ability of dogs to respond to commands, (and not their sense of smell or vision) you want to make the two balls as distinct as possible (to the dog) so that you can be sure a failed result comes from training, and not from being unable to distinguish the two balls.

They're not really colorblind, just much lower visual acuity than humans.

Even at grayscale differentiation based on luminance is possible.

And then there's their sense of smell, they very well could smell the chemical differences between red and green pigment compounds.

You can have a red object and a green object of the same luminance, which are indistinguishable on panchromatic film. (I'm assuming here that the term luminance incorporates the spectral response of the human eye, or dog as the case may be).

Dogs only have receptors with peaks at two frequencies, not three, IIRC, so have a more limited palette. They may be better at motion detection, and are as good or better than us at speed and vector determination: they can organize a hunt over a surface of the earth, and bring down moving prey. They may also be better at edge detection.